About The Missing 90 Minutes by Dean Mcdonald
Almost everyone measures sleep by duration, and almost everyone is measuring the wrong thing. Nine hours in bed with thirty minutes of deep sleep produces a wrecked day. Seven hours with ninety minutes of deep sleep produces a day where you feel a decade younger. Same person, same bed, opposite outcome. Dean Mcdonald spent twenty-eight years in networking, software, and AI: two decades of hotel rooms, deployment windows at two in the morning, and late calls across time zones. He wore two sensors continuously and never opened either dashboard. When he finally looked, the number that separated a good day from a write-off was minutes of slow-wave sleep, not hours asleep. The book takes apart the eight-hour rule and where it came from, explains what the body does during deep sleep and what interferes with it, is honest about how imprecise consumer trackers are, and closes every chapter with something practical to act on. No miracle fixes, no products to chase. Written for people who follow the rules, get their eight hours, and still wake up tired. FREE on Kindle August 21 to 23, 2026.
